According to thefood historian Alan Davidson, our sweet dessert jellies started out as a savoury dish made by medieval cooks from calves’ feet and other meat stocks. The first recorded use of the word “jelly” is in a 15th-century poem “The Debate of the Horse, Goose and Sheep” by John Lydgate: “The shepe… of whos hede boylled…Ther cometh a gely”.

“Leach” was a popular confection made with milk, almonds, sugar and rosewater and set with isinglass. “Flummery” was made by steeping oatmeal in water, boiling the strained liquor with sugar and leaving it to set in decorated sycamore moulds.

Through the 18th and 19th centuries ceramic and copper jelly moulds became ever more elaborate: the wobbling towers, castles, obelisks and lions on pedestals they created were often used as centrepieces for feasts and dinner parties.

Gel

Today, jelly usually means fruit jelly, and the most common gelling agent is gelatin. The word comes from the Latin gelare, meaning “to freeze”.

Gelatinis made of long strings of proteins known as polymers released from the collagen in the skin, bones and connective tissue of animals as it is broken down by heat and water. Dissolved in water and cooled, it forms a “gel”, a word first coined by the 19th-century Scottish chemist Thomas Graham, through shortening “gelatin”. A gel has the density and weight of a liquid, but acts like a solid because of the internal cross-linking of polymer chains. That’s why jellies wobble – tap one and the energy passes through it like ripples across a liquid. As soon as heat is applied, these cross-linkings untangle themselves, the surface tension breaks, and the gel returns to its liquid state.

The melting point of gelatin is about 35C (95F), i.e. below our body temperature, which is why jelly dissolves in our mouths.

Almost half of the gelatin produced each year comes from pig skin. Other uses include the casings of pharmaceutical drug capsules, gloss finishes on the surface of paper, binding match heads and sandpaper and “knoxing” the hair of synchronised swimmers so it stays in place (Knox is an American gelatin maker).

Sweet

Jelly babies used to be calledPeace Babies, and were made to commemorate the end of the First World War. An even earlier version called Unclaimed Babies were made in the 1860s by a company called Fryer’s. Almost eight out of 10 people bite the heads off their jelly babies.

Ronald Reagan loved jellybeans so much that American confectionery company Jelly Belly created a blueberry flavour so Reagan could serve red, white and blue beans at his parties. He also used them as a basic form of psychometric testing: “You can tell a lot about a fella’s character by whether he picks out all of one colour or just grabs a handful.”

Alive

Jelly gives the same reading on an electroencephalography (EEG) machine, used to measure brain activity, as a human brain. Jellies show the same rhythms that human brains display when the person is awake but has their eyes closed. Going by the EEG results, a jelly would qualify as alive enough to not have its life support machine turned off. The jelly appears to absorb electro-magnetic signals from the machinery in the room which gives it these “alive” readings.

Starshot

Star jelly is a mysterious gelatinous substancethat appears suddenly in clumps, often under trees. It has been recorded since the 14th century under many different names including star-fallen, star-falling, star-shot, star-slime, star-slough, star-slubber and star-slutch. The Mexicans call it caca de luna (“moon s***”). No one is sure what it is, but a 1948 article in Scientific American described people finding a 4ft-wide pool of jelly next to a meteorite. This bolstered the belief that it might have fallen from space. Other theories favour regurgitated frogs’ ovaries (deposited by passing birds), stag semen or unfertilised frogspawn. The most likely explanation is that it’s a type of algae called nostoc, which is usually invisible but swells up into a jellylike mass when mixed with rainwater.

Jellygraph

Jelly can be used as a photocopier. Thejellygraph (or hectograph) works by making images on a tray of set gelatin using a special ink. Ordinary paper can then be laid on top, and multiple copies of the image taken. It’s a low-tech piece of kit but does render the jelly inedible.